Last Updated: June 24, 2022

Not only are they lightweight, easy to process, strong, inexpensive and transparent; some of them (like the OKP polyesters) have high refractive index.
High refractive index??
Refractive index is a measure of how light propagates through a material. The higher the refractive index the slower the light travels, which causes a correspondingly increased change in the direction of the light within the material. What this means for lenses is that a higher refractive index material can bend the light more and allow the profile of the lens to be lower.
So the lens gets thinner (see the graphic below). Decreasing lens thickness corresponds to decreased weight (always a good thing), and continuation of the engineering goal that each generation of electronics must be smaller than the one before.
It also enables some of the fashions we have these days.
How else can you carry a phone in the pocket of your “skinny jeans”?
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